fix #389 review round: settings v3 FOV migration + live apply; AD-90

Dual-lens Opus review of 7e0c1303 (reports committed under
docs/research/). The law, gate, and vertical application are CONFIRMED
at instruction-byte level against the PDB-paired acclient.exe (the BN
text FPU-elides this whole area); the fix round addresses the findings:

- Blast MUST-FIX 1: real schema migration instead of a hand-edited dev
  file. SettingsStore v2->v3: a pre-v3 display.fieldOfView was the
  applied vertical FOV in degrees; v3 means retail's m_fGameFOV.
  LoadDisplay migrates on read - the untouched old default 60 maps to
  the retail default 90; a deliberate other value preserves its visible
  16:9 framing (x (16/9 - 0.1)), clamped to the registered [10,160];
  the next save stamps v3 and migration never reruns. The dev
  settings.json hand-edit was reverted so the migration owns it.
- Blast MUST-FIX 2 / mechanism M2: the Field of View now applies LIVE on
  Save (retail: Render::GRPCallback_OnRenderPreferenceChanged @0x0054d999
  -> SmartBox::SetDefaultFov). RuntimeSettingsTargets gains the camera
  graph and applies through ApplyDisplayWindowState - the update-phase
  seam, deliberately NOT the render-phase preview path (the review's
  WATCH-3 cull-vs-raster landmine).
- Mechanism M1 -> register row AD-90: retail's divisor aspect runs
  through the Render.AspectRatio preference (ComputeAspectForViewport
  @0x0054f150, (w/h) x pref x 0.75) - exactly raw w/h at the registered
  default, which is what acdream assumes; retail's NaN-through-the-gate
  quirk (M3) is folded into the same row as deliberately not reproduced.
- Docs: RetailFieldOfView now cites the decisive vertical proof
  (D3DXMatrixPerspectiveFovLH fovy slot @0x0059ab71), the unconditional
  SmartBox::RenderNormalMode site, and M4's exact horizontal numbers
  (89.0/83.9/80.6 deg); the Config FOV row comment updated to LIVE.
- Blast WATCH 4 disposition: the 15 replay-harness PI/3 constants stay -
  they are CAPTURE-TIME camera parameters for recorded fixtures, not
  production framing; changing them would invalidate the replays.

Tests: +6 SettingsStore migration facts, +1 live-apply fact.
App suite 4,962/3 skips; UI.Abstractions 922.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/AcDream.App/UI/Layout/ConfigOptionsPageController.cs

@@ -575,10 +575,11 @@ public static class ConfigOptionsPageController
             storeOnly: true, // TS-74
             rangeLowKey: "ID_Graphics_Value_Slow", rangeHighKey: "ID_Graphics_Value_Fast");
 
-        // Field of View: NEXT-LAUNCH via DisplaySettings.FieldOfView + the
-        // existing RuntimeSettingsController.ApplyStartup path — matches
-        // the pre-existing (dev-tools Settings panel era) behaviour, not a
-        // new gap this slice introduces.
+        // Field of View: LIVE as of the #389 fix round — the stored value is
+        // retail's m_fGameFOV in degrees and applies on Save through
+        // RuntimeSettingsTargets.ApplyDisplayWindowState (retail applies its
+        // FOV preference live too: Render::GRPCallback_OnRenderPreferenceChanged
+        // @0x0054d999 → SmartBox::SetDefaultFov).
         BuildSliderRow(
             listBox, RangedSliderTemplateIndex, "ID_Graphics_FieldOfView",
             min: 10f, max: 160f, defaultValue: 90.0f, page, resolveString,